Immune cell products with homogenous expression of tumor targeting chimeric antigen receptors (CARs) are desirable for clinical evaluation of adoptive therapy strategies to eliminate the product-to-product variability of transgene expression otherwise intrinsic to transduction and other genetic modification procedures without subsequent selection. Immunotherapy using genetically redirected immune cells is an attractive approach for treating minimal residual disease in a variety of cancer patients. However, immunologic rejection of cell products expressing antibiotic selection proteins as part of the transduction strategy has impeded this strategy. A novel selection marker that is not expressed on human lymphocytes, does not contain endogenous signaling or trafficking function, and is recognized by a known, preferably commercially available, pharmaceutical grade antibody reagent that can be utilized for selection, in vivo tracking, and depletion of transduced cells would be a significant improvement in the art.